Some interesting info.
http://www.those-who-serve.com/2017/07/29/ford-explorer-carbon-monoxide/
Also
https://www.policeone.com/police-pr...airs-Austin-police-SUVs-but-questions-linger/
"But Ford is still investigating why many non-police consumers have also complained to the automaker and the government about exhaust fumes — which contain odorless, colorless carbon monoxide as well as sulfur and other chemicals — in their vehicles. It also can't explain why there have been no carbon monoxide complaints about a rival SUV, the Chevrolet Tahoe, which is also used by police."
"But Ford clearly knows it has a problem with non-police Explorers. It has issued two bulletins to dealers — in December and March — telling them how to repair vehicles with exhaust in their cabins, and has told customers with concerns to take their Explorers to a dealer. It also settled a class action lawsuit over the issue in Florida last fall.
The National Highway Traffic Safety Administration has found more than 2,700 complaints of exhaust odors in the passenger compartment in an investigation started a year ago. Among the complaints were three crashes and 41 injuries, mostly loss of consciousness, nausea and headaches. Many — but not all — of the complaints came from police departments."
"Gubing said the problem isn't found in police cars like the Ford Taurus because the exhaust is usually trapped in the trunk. But he couldn't explain why police departments haven't complained about the Chevrolet Tahoe, which is also fitted with extra equipment. Darrel Stephens, head of the Major Cities Police Chiefs Association, said he hasn't heard about exhaust problems in the Tahoe.
"I wish I could comment on their product design, but I don't have that," Gubing said. "This is not a Ford-specific design problem."
Gubing also said Ford has ruled out cracks in the exhaust manifold as a cause of the problem. NHTSA says tiny cracks in the manifold — a cast iron or stainless steel tube that carries combustion gasses to the exhaust — could explain why exhaust is entering the cabin. But Gubing said there is no pathway for exhaust to escape from the manifold and into the car."
I hadn't thought about it until now, but my 2005 Grand Cherokee had broken exhaust manifold bolts, at the rear of the manifold, on both sides of the engine. I never smelled a thing. I only knew because of the noise. I drove it that way longer than I've owned the Explorer.
My friend and I poked around, and couldn't find any signs of cracks or other damage in the exhaust system. When I demonstrated the issue, he was shocked by how strong the smell was.
There are work days that I spend 10-40 minutes out of each hour in the Explorer. On those days, especially if I have been driving it hard, I start to feel sick by the end of the day. FIrst it's a headache, then I'll get lightheaded and nauseous. I have to be careful to remember to open the windows and clear it out periodically.
Something that I've noticed, that I haven't seen any comments on, is that this issue seems to be more prevalent in hotter climates. A bunch in Texas, and we've had a few pulled in South Carolina, but the one in Mass didn't happen until the peak of the summer. I bought mine in January, and couldn't demonstrate the issue until late March, when it got hot. So, it seems that ambient temperature has some sort of affect on the issue.